There have been conventionally known outboard motors which include oil filters for filtering engine oil, such as the one disclosed in Japanese Patent Application Laid-Open Publication No. 2005-343226 (JP 2005-343226 A). FIGS. 7 and 8 hereof show the outboard motor disclosed in JP 2005-343226 A.
Referring to FIG. 7, an outboard motor 100 as an example of the prior art is designed so that the oil collected in an oil pan 102 of a longitudinal engine 101 in which the crankshaft is longitudinally oriented is suctioned up by an oil pump and filtered by an oil filter 103. The filtered oil is supplied to top and bottom bearings of the crankshaft via a main gallery which is an oil passage disposed vertically within a cylinder block 104, and is also supplied to a camshaft of the engine 101, whereby these components can be appropriately lubricated.
The oil filter 103 is replaced either periodically or after a specified amount of use. FIG. 8 is used to describe the oil filter replacement procedure normally performed with an outboard motor.
According to FIG. 8, the oil filter 103 is removed and a new oil filter 103 is installed. The oil filter 103 is installed in a removable manner in the cylinder block 104 so as to be positioned in the vertical center of the main gallery 105. When the oil filter 103 is removed, the oil above the oil filter 103 from the oil that has accumulated in the main gallery 105 flows out to the exterior through a filter attachment hole 106 as shown by arrow (1). An operator must wipe up the leaked oil, and the operation is troublesome. Therefore, there is a demand for an engine for an outboard motor in which the oil filter can be replaced without the oil flowing out to the exterior.